Methods of forming a nanostructured polymer material including block copolymer materials

ABSTRACT

Methods for fabricating sub-lithographic, nanoscale microstructures utilizing self-assembling block copolymers, and films and devices formed from these methods are provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/104,304, filed Dec. 12, 2013, now U.S. Pat. No. 9,315,609, issuedApr. 19, 2016, which is a divisional of U.S. patent application Ser. No.13/469,697, filed May 11, 2012, now U.S. Pat. No. 8,633,112, issued Jan.21, 2014, which is a continuation of U.S. patent application Ser. No.12/052,956, filed Mar. 21, 2008, now U.S. Pat. No. 8,426,313, issuedApr. 23, 2013.

TECHNICAL FIELD

Embodiments of the invention relate to methods of fabricating thin filmsof self-assembling block copolymers, and devices resulting from thosemethods.

BACKGROUND OF THE INVENTION

As the development of nanoscale mechanical, electrical, chemical andbiological devices and systems increases, new processes and materialsare needed to fabricate nanoscale devices and components. Makingelectrical contacts to conductive lines has become a significantchallenge as the dimensions of semiconductor features shrink to sizesthat are not easily accessible by conventional lithography. Opticallithographic processing methods have difficulty fabricating structuresand features at the sub-60 nanometer level. The use of self-assemblingdiblock copolymers presents another route to patterning at nanoscaledimensions. Diblock copolymer films spontaneously assembly into periodicstructures by microphase separation of the constituent polymer blocksafter annealing, for example, by thermal annealing above the glasstransition temperature of the polymer or by solvent annealing, formingordered domains at nanometer-scale dimensions.

The film morphology, including the size and shape of themicrophase-separated domains, can be controlled by the molecular weightand volume fraction of the AB blocks of a diblock copolymer to producelamellar, cylindrical, or spherical morphologies, among others. Forexample, for volume fractions at ratios greater than about 80:20 of thetwo blocks (AB) of a diblock polymer, a block copolymer film willmicrophase separate and self-assemble into periodic spherical domainswith spheres of polymer B surrounded by a matrix of polymer A. Forratios of the two blocks between about 60:40 and 80:20, the diblockcopolymer assembles into a periodic hexagonal close-packed or honeycombarray of cylinders of polymer B within a matrix of polymer A. For ratiosbetween about 50:50 and 60:40, lamellar domains or alternating stripesof the blocks are formed. Domain size typically ranges from 5-50 nm.

Many applications of the self-assembly of block copolymers (BCPs) tolithography require that the self-assembled domains orient perpendicularto the substrate with both domains wetting and exposed at the airinterface. With selective removal of one of the polymer blocks to forman etch mask, the perpendicularly oriented void structures can then beused for etching the underlying substrate.

Conventional thermal annealing of most BCPs (e.g., PS-b-PVP, etc.) inair or vacuum will typically result in one block preferentially wettingthe air vapor interface. A variant of thermal annealing called zoneannealing, can provide rapid self-assembly (e.g., on the order ofminutes) but is only effective for a small number of BCPs (e.g.,PS-b-PMMA, PS-b-PLA) with polymer domains that equally wet the air vaporinterface. Solvent annealing of BCPs has been used to produce aperpendicular orientation of the self-assembled domains to thesubstrate, but is generally a very slow process, typically on the orderof days, and can require large volumes of the solvent. A typical solventanneal is conducted by exposing a BCP film to a saturated solventatmosphere at 25° C. for at least 12 hours (often longer).

It would be useful to provide methods of fabricating films of arrays ofordered nanostructures that overcome these problems.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described below with reference to thefollowing accompanying drawings, which are for illustrative purposesonly. Throughout the following views, reference numerals will be used inthe drawings, and the same reference numerals will be used throughoutthe several views and in the description to indicate same or like parts.

FIG. 1 illustrates a diagrammatic top plan view of a portion of asubstrate at a preliminary processing stage according to an embodimentof the present disclosure, showing the substrate with a neutral wettingmaterial thereon. FIGS. 1A and 1B are elevational, cross-sectional viewsof the substrate depicted in FIG. 1 taken along lines 1A-1A and 1B-1B,respectively.

FIG. 2 illustrates a diagrammatic top plan view of the substrate of FIG.1 at a subsequent stage showing the formation of trenches in a materiallayer formed on the neutral wetting material. FIGS. 2A and 2B illustrateelevational, cross-sectional views of a portion of the substratedepicted in FIG. 2 taken, respectively, along lines 2A-2A and 2B-2B.

FIG. 3 illustrates a side elevational view of a portion of a substrateat a preliminary processing stage according to another embodiment of thedisclosure, showing the substrate with trenches in a material layerformed on the substrate.

FIG. 4 illustrates a side elevational view of the substrate of FIG. 3 ata subsequent stage showing the formation of a neutral wetting materialwithin the trenches.

FIG. 5 is a diagrammatic top plan view of the substrate of FIG. 2 at asubsequent stage showing a block copolymer material within the trenches.FIGS. 5A and 5B illustrate elevational, cross-sectional views of aportion of the substrate depicted in FIG. 5 taken along lines 5A-5A and5B-5B, respectively.

FIGS. 6-8 are diagrammatic top plan views of the substrate of FIG. 5 atsubsequent stages showing annealing of a portion of the film accordingto an embodiment of the invention by a zoned annealing technique. FIGS.6A-8A illustrate elevational, cross-sectional views of the substratedepicted in FIGS. 6-8 taken along lines 6A-6A, 7A-7A and 8A-8A,respectively, showing an embodiment of a heating device for zoneannealing the film. FIG. 6B is an elevational, cross-sectional view ofthe substrate depicted in FIG. 6 taken along lines 6B-6B.

FIG. 9 is a top plan view of the substrate of FIG. 5 at a subsequentstage according to another embodiment of a method of the invention,illustrating placement of a non-preferential wetting material over theblock copolymer material during an anneal. FIGS. 9A and 9B areelevational, cross-sectional views of the substrate depicted in FIG. 9taken along lines 9A-9A and 9B-9B, respectively.

FIGS. 10A and 10B are cross-sectional views of the substrate shown inFIGS. 9A and 9B, respectively, at a subsequent stage showing theannealed, self-assembled block copolymer material, and removal of thenon-preferential wetting material after the anneal.

FIGS. 11-13 are top plan views of the substrate of FIG. 8 at subsequentstages, illustrating an embodiment of the use of the self-assembledblock copolymer film after removal of one of the polymer blocks, as amask to etch the substrate and filling of the etched openings. FIGS.11A-13A illustrate elevational, cross-sectional views of a portion ofthe substrate depicted in FIGS. 11-13 taken along lines 11A-11A to13A-13A, respectively.

FIGS. 11B-13B are cross-sectional views of the substrate depicted inFIGS. 11-13 taken along lines 11B-11B to 13B-13B, respectively.

DETAILED DESCRIPTION OF THE INVENTION

The following description with reference to the drawings providesillustrative examples of devices and methods according to embodiments ofthe invention. Such description is for illustrative purposes only andnot for purposes of limiting the same.

In the context of the current application, the terms “semiconductorsubstrate,” or “semiconductive substrate,” or “semiconductive waferfragment,” or “wafer fragment,” or “wafer,” will be understood to meanany construction comprising semiconductor material including, but notlimited to, bulk semiconductive materials such as a semiconductor wafer(either alone or in assemblies comprising other materials thereon), andsemiconductive material layers (either alone or in assemblies comprisingother materials). The term “substrate” refers to any supportingstructure including, but not limited to, the semiconductive substrates,wafer fragments or wafers described above.

“L_(o)” as used herein is the inherent periodicity or pitch value (bulkperiod or repeat unit) of structures that self-assemble upon annealingfrom a self-assembling (SA) block copolymer. “L_(B)” as used herein isthe periodicity or pitch value of a blend of a block copolymer with oneor more of its constituent homopolymers. “L” is used herein to indicatethe center-to-center cylinder pitch or spacing of cylinders of the blockcopolymer or blend, and is equivalent to “L_(o)” for a pure blockcopolymer and “L_(B)” for a copolymer blend.

In embodiments of the invention, a polymer material (e.g., film, layer)is prepared by guided self-assembly of block copolymers, with bothpolymer domains at the air interface. The block copolymer materialspontaneously assembles into periodic structures by microphaseseparation of the constituent polymer blocks after annealing, formingordered domains of perpendicular-oriented cylinders at nanometer-scaledimensions within a trench.

A method for fabricating a self-assembled block copolymer material thatdefines a one-dimensional (1D) array of nanometer-scale,perpendicular-oriented cylinders according to an embodiment of theinvention is illustrated with reference to FIGS. 1-8.

The described embodiment involves a thermal anneal of acylindrical-phase block copolymer under a solvent atmosphere. The annealis conducted in combination with a graphoepitaxy technique that utilizesa lithographically defined trench as a guide with a floor composed of amaterial that is neutral wetting to both polymer blocks, and sidewallsand ends that are preferential wetting to one polymer block and functionas constraints to induce the block copolymer to self-assemble into anordered 1D array of a single row of cylinders in a polymer matrixoriented perpendicular to the trench floor and registered to the trenchsidewalls. In some embodiments, two or more rows ofperpendicular-oriented cylinders can be formed in each trench.

As depicted in FIGS. 1-1B, a substrate 10 is provided, which can besilicon, silicon oxide, silicon nitride, silicon oxynitride, siliconoxycarbide, among other materials. As further depicted, conductive lines12 (or other active area, e.g., semiconducting regions) are situatedwithin the substrate 10.

In any of the described embodiments, a single trench or multipletrenches can be formed in the substrate, and can span the entire widthof an array of lines (or other active area). In embodiments of theinvention, the substrate 10 is provided with an array of conductivelines 12 (or other active areas) at a pitch of L. The trench or trenchesare formed over the active areas 12 (e.g., lines) such that when theblock copolymer material is annealed, each cylinder will be situatedabove a single active area 12 (e.g., a conductive line). In someembodiments, multiple trenches 18 are formed with the ends 24 of eachadjacent trench 18 aligned or slightly offset from each other at lessthan 5% of L such that cylinders in adjacent trenches 18 are aligned andsituated above the same conductive line 12.

In the illustrated embodiment, a neutral wetting material 14 (e.g.,random copolymer) has been formed over the substrate 10. A materiallayer 16 (or one or more material layers) can then be formed over theneutral wetting material 14 and etched to form trenches 18 that areoriented perpendicular to the array of conductive lines 12, as shown inFIGS. 2-2B. Portions of the material layer 16 form a spacer 20 outsideand between the trenches. The trenches 18 are structured with opposingsidewalls 22, opposing ends 24, a floor 26, a width (w_(t)), a length(l_(t)) and a depth (D_(t)).

In another embodiment, the material layer 16′ can be formed on thesubstrate 10′, etched to form the trenches 18′ as depicted in FIG. 3,and a neutral wetting material 14′ can then be formed on the trenchfloors 26′ as shown in FIG. 4. For example, a random copolymer materialcan be deposited into the trenches 18′ and crosslinked to form a neutralwetting material layer. Material on surfaces outside the trenches 18′such as on the spacers 20′ (e.g., non-crosslinked random copolymer) canbe subsequently removed.

Single or multiple trenches 18 (as shown) can be formed using alithographic tool having an exposure system capable of patterning at thescale of L (10-100 nm). Such exposure systems include, for example,extreme ultraviolet (EUV) lithography, proximity X-rays and electronbeam (E-beam) lithography, as known and used in the art. Conventionalphotolithography can attain (at smallest) about 58 nm features.

A method called “pitch doubling” or “pitch multiplication” can also beused for extending the capabilities of photolithographic techniquesbeyond their minimum pitch, as described, for example, in U.S. Pat. No.5,328,810 (Lowrey et al.), U.S. Pat. No. 7,115,525 (Abatchev, et al.),U.S. Patent Publication 2006/0281266 (U.S. Pat. No. 7,396,781, issuedJul. 8, 2008, to Wells) and U.S. Patent Publication 2007/0023805 (U.S.Pat. No. 7,776,715, issued Aug. 17, 2010, to Wells). Briefly, a patternof lines is photolithographically formed in a photoresist materialoverlying a layer of an expendable material, which in turn overlies asubstrate, the expendable material layer is etched to form placeholdersor mandrels, the photoresist is stripped, spacers are formed on thesides of the mandrels, and the mandrels are then removed, leaving behindthe spacers as a mask for patterning the substrate. Thus, where theinitial photolithography formed a pattern defining one feature and onespace, the same width now defines two features and two spaces, with thespaces defined by the spacers. As a result, the smallest feature sizepossible with a photolithographic technique is effectively decreaseddown to about 30 nm or less.

Factors in forming a single 1D array or layer of perpendicular-orientednanocylinders within the trenches include the width (w_(t)) and depth(D_(t)) of the trench, the formulation of the block copolymer or blendto achieve the desired pitch (L), and the thickness (t) of the blockcopolymer material within the trench.

There is a shift from two rows to one row of the perpendicular cylinderswithin the center of the trench 18 as the width (w_(t)) of the trench 18is decreased and/or the periodicity (L value) of the block copolymer isincreased, for example, by forming a ternary blend by the addition ofboth constituent homopolymers. The boundary conditions of the trenchsidewalls 22 in both the x- and y-axis impose a structure wherein eachtrench 18 contains “n” number of features (e.g., cylinders). Forexample, a block copolymer or blend having a pitch or L value of 35-nmdeposited into a 75-nm wide trench 18 having a neutral wetting floorwill, upon annealing, result in a zigzag pattern of 17.5-nm diameter(≅0.5*L) perpendicular cylinders that are offset by about one-half thepitch distance (about 0.5*L) for the length (l_(t)) of the trench 18,rather than a single line row of perpendicular cylinders aligned withthe sidewalls 22 down the center of the trench 18.

In the illustrated embodiment, the trenches 18 are constructed with awidth (w_(t)) of about 1.5-2*L (or 1.5-2× the pitch value) of the blockcopolymer such that a cast block copolymer material (or blend) of aboutL will self-assemble upon annealing into a single row of perpendicularcylinders (diameter≅0.5*L) with a center-to-center pitch distance (p) ofadjacent cylinders at or about L. For example, in using a cylindricalphase block copolymer with an about 50 nm pitch value or L, the width(w_(t)) of the trenches 18 can be about 1.5-2*50 nm or about 75-100 nm.The length (l_(t)) of the trenches 18 is at or about n*L or an integermultiple of L, typically within a range of about n*10 to about n*100 nm(with n being the number of features or structures, e.g., cylinders).The depth (D_(t)) of the trenches 18 is greater than or equal to L(D_(t)>L). The width of the spacers 20 between adjacent trenches canvary and is generally about L to about n*L. In some embodiments, thetrench dimension is about 20-100 nm wide (w_(t)) and about 100-25,000 nmin length (l_(t)), with a depth (D_(t)) of about 10-100 nm.

A self-assembling, cylindrical-phase block copolymer material 28 havingan inherent pitch at or about L_(o) (or a ternary blend of blockcopolymer and homopolymers blended to have a pitch at or about L_(B)) isdeposited into the trenches 18, typically as a film (as in FIGS. 5-5B).

The block copolymer (or blend) is constructed such that all of thepolymer blocks will have equal preference for a neutral wetting materialon the trench floor. The block copolymer material can be constructed toprovide desired properties such as defect tolerance and ease ofdevelopment and/or removal of one of the blocks. In some embodiments ofthe invention, the block copolymer or blend is constructed such that theminor domain can be selectively removed.

Examples of diblock copolymers include, for example,poly(styrene)-b-poly(vinylpyridine) (PS-b-PVP),poly(styrene)-b-poly(methyl methacrylate) (PS-b-PMMA) or otherPS-b-poly(acrylate) or PS-b-poly(methacrylate),poly(styrene)-b-poly(lactide) (PS-b-PLA),poly(styrene)-b-poly(tert-butyl acrylate) (PS-b-PtBA), andpoly(styrene)-b-poly(ethylene-co-butylene (PS-b-(PS-co-PB)),poly(styrene)-b-poly(ethylene oxide) (PS-b-PEO),poly(isoprene)-b-poly(ethyleneoxide) (PI-b-PEO),poly(isoprene)-b-poly(methyl methacrylate) (PI-b-PMMA),poly(butadiene)-b-poly(ethyleneoxide) (PBD-b-PEO), a PS-b-PEO blockcopolymer having a cleavable junction such as a triphenylmethyl (trityl)ether linkage between PS and PEO blocks (optionally complexed with adilute concentration (e.g., about 1 wt %) of a salt such as KCl, KI,LiCl, LiI, CsCl or CsI (Zhang et al., Adv. Mater. 2007, 19, 1571-1576),a PS-b-PMMA block copolymer doped with PEO-coated gold nanoparticles ofa size less than the diameter of the self-assembled cylinders (Park etal., Macromolecules, 2007, 40(11), 8119-8124), and apoly(styrene)-b-poly(2-vinylpyridine) (PS-b-P2VP) block copolymer havinga cleavable junction such as a dithiol group, among others, withPS-b-PVP used in the illustrated embodiment. Other types of blockcopolymers (i.e., triblock or multiblock copolymers) can be used.Examples of triblock copolymers include ABC copolymers such aspoly(styrene-b-methyl methacrylate-b-ethylene oxide) (PS-b-PMMA-b-PEO),and ABA copolymers, such as PS-PMMA-PS, PMMA-PS-PMMA, and PS-b-PI-b-PS,among others.

The film morphology, including the domain sizes and periods (L_(o)) ofthe microphase-separated domains, can be controlled by chain length of ablock copolymer (molecular weight, MW) and volume fraction of the ABblocks of a diblock copolymer to produce cylindrical morphologies (amongothers). For example, for volume fractions at ratios of the two blocksgenerally between about 60:40 and 80:20 (A:B), the diblock copolymerwill microphase separate and self-assemble into periodic cylindricaldomains of polymer B within a matrix of polymer A. An example of acylinder-forming PS-b-PVP copolymer material (L_(o)˜28 nm) to form about14 nm diameter cylindrical PVP domains in a matrix of PS is composed ofabout 70 wt % PS and 30 wt % PVP with a total molecular weight (M_(n))of 44.5 kg/mol. An example of a cylinder-forming PS-b-PMMA copolymermaterial (L_(o)=35 nm) to form about 20 nm diameter cylindrical PMMAdomains in a matrix of PS is composed of about 70 wt % PS and 30 wt %PMMA with a total molecular weight (M_(n)) of 67 kg/mol. As anotherexample, a PS-b-PLA copolymer material (L=49 nm) can be composed ofabout 71 wt % PS and 29 wt % PLA with a total molecular weight (M_(n))of about 60.5 kg/mol to form about 27 nm diameter cylindrical PLAdomains in a matrix of PS.

The L value of the block copolymer can be modified, for example, byadjusting the molecular weight of the block copolymer. The blockcopolymer material can also be formulated as a binary or ternary blendcomprising a block copolymer and one or more homopolymers (HPs) of thesame type of polymers as the polymer blocks in the block copolymer, toproduce a blend that will swell the size of the polymer domains andincrease the L value. The concentration of homopolymers in the blend canrange from 0 to about 60 wt %.

An example of a ternary diblock copolymer blend is a PS-b-P2VP/PS/P2VPblend, for example, 60 wt % of 32.5 K/12 K PS-b-P2VP, 20 wt % of 10 KPS, and 20 wt % of 10 K P2VP. Another example of a ternary diblockcopolymer blend is a PS-b-PMMA/PS/PMMA blend, for example, 60 wt % of46K/21K PS-b-PMMA, 20 wt % of 20K polystyrene and 20 wt % of 20Kpoly(methyl methacrylate). Yet another example is a blend of 60:20:20(wt %) of PS-b-PEO/PS/PEO, or a blend of about 85-90 wt % PS-b-PEO andup to 10-15 wt % PEO; it is believed that the added PEO homopolymer mayfunction, at least in part, to lower the surface energy of the PEOdomains to that of PS.

In the present embodiment, the trench floors 26 are structured to beneutral wetting (equal affinity for both blocks of the copolymer) toinduce formation of cylindrical polymer domains that are orientedperpendicular to the trench floors 26, and the trench sidewalls 22 andends 24 are structured to be preferential wetting by one block of theblock copolymer to induce registration of the cylinders to the sidewalls22 as the polymer blocks self-assemble. In response to the wettingproperties of the trench surfaces, upon annealing, the preferred orminority block of the cylindrical-phase block copolymer willself-assemble to form a single row of cylindrical domains in the centerof a polymer matrix for the length of the trench and segregate to thesidewalls and edges of the trench to form a thin interface brush orwetting layer (e.g., as in FIGS. 6-6B). Entropic forces drive thewetting of a neutral wetting surface by both blocks, and enthalpicforces drive the wetting of a preferential-wetting surface by thepreferred block (e.g., the minority block).

To provide preferential wetting surfaces, for example, in the use of aPS-b-PVP (or PS-b-PMMA, etc.) block copolymer, the material layer 16 canbe composed of silicon (with native oxide), oxide (e.g., silicon oxide,SiO_(x)), silicon nitride, silicon oxycarbide, indium tin oxide (ITO),silicon oxynitride, and resist materials such as methacrylate-basedresists and polydimethylglutarimide resists, among other materials,which exhibit preferential wetting toward the PVP (or PMMA, etc.) block.In the use of a PS-b-PVP cylinder-phase block copolymer material, forexample, the block copolymer material will self-assemble to form a thininterface layer and cylinders of PVP in a PS matrix.

In other embodiments, a preferential wetting material such as apolymethyl methacrylate (PMMA) polymer modified with an —OH containingmoiety (e.g., hydroxyethylmethacrylate) can be applied onto the surfacesof the trenches, for example, by spin-coating and then heating (e.g., toabout 170° C.) to allow the terminal OH groups to end-graft to oxidesidewalls 22 and ends 24 of the trenches 18. Non-grafted material can beremoved by rinsing with an appropriate solvent (e.g., toluene). See, forexample, Mansky et al., Science, 1997, 275, 1458-1460, and In et al.,Langmuir, 2006, 22, 7855-7860.

A neutral wetting trench floor 26 allows both blocks of the copolymermaterial to wet the floor 26 of the trench 18. A neutral wettingmaterial 14 can be provided by applying a neutral wetting polymer (e.g.,a neutral wetting random copolymer) onto the substrate 10, forming thematerial layer 16 and then etching the trenches 18 to expose theunderlying neutral wetting material, as illustrated in FIGS. 2-2B.

In another embodiment illustrated in FIGS. 3 and 4, a neutral wettingrandom copolymer material can be applied after forming the trenches 18′,for example, as a blanket coat by casting or spin-coating into thetrenches 18′, as depicted in FIG. 4. The random copolymer material canthen be thermally processed to flow the material into the bottom of thetrenches 18′ by capillary action, which results in a layer (mat) 14′composed of the crosslinked, neutral wetting random copolymer. Inanother embodiment, the random copolymer material within the trenches18′ can be photo-exposed (e.g., through a mask or reticle) to crosslinkthe random copolymer within the trenches 18′ to form the neutral wettingmaterial 14′. Non-crosslinked random copolymer material outside thetrenches (e.g., on the spacers 20′) can be subsequently removed.

Neutral wetting surfaces can be specifically prepared by the applicationof random copolymers composed of monomers identical to those in theblock copolymer and tailored such that the mole fraction of each monomeris appropriate to form a neutral wetting surface. For example, in theuse of a PS-b-PVP block copolymer, a neutral wetting material 14 can beformed from a thin film of a photo-crosslinkable random PS-r-PVP thatexhibits non-preferential or neutral wetting toward PS and PVP, whichcan be cast onto the substrate 10 (e.g., by spin-coating). The randomcopolymer material can be fixed in place by chemical grafting (on anoxide substrate) or by thermally or photolytically crosslinking (anysurface) to form a mat that is neutral wetting to PS and PVP andinsoluble when the block copolymer material is cast onto it, due to thecrosslinking. In another example, in the use of PS-b-PMMA, aphoto-crosslinkable PS-r-PMMA random copolymer (e.g., containing anabout 0.6 mole fraction of styrene) can be used.

In embodiments in which the substrate 10 is silicon (with native oxide),another neutral wetting surface for PS-b-PMMA can be provided byhydrogen-terminated silicon. The floors 26 of the trenches 18 can beetched, for example, with a hydrogen plasma, to remove the oxidematerial and form hydrogen-terminated silicon, which is neutral wettingwith equal affinity for both blocks of a block copolymer material.H-terminated silicon can be prepared by a conventional process, forexample, by a fluoride ion etch of a silicon substrate (with nativeoxide present, about 12-15 Å) by exposure to an aqueous solution ofhydrogen fluoride (HF) and buffered HF or ammonium fluoride (NH₄F), byHF vapor treatment, or by a hydrogen plasma treatment (e.g., atomichydrogen).

An H-terminated silicon substrate can be further processed by grafting arandom copolymer such as PS-r-PVP, PS-r-PMMA, etc. selectively onto thesubstrate resulting in a neutral wetting surface for the correspondingblock copolymer (e.g., PS-b-PVP, PS-b-PMMA, etc.). For example, aneutral wetting layer of a PS-r-PMMA random copolymer can be provided byan in situ free radical polymerization of styrene and methylmethacrylate using a di-olefinic linker such as divinyl benzene, whichlinks the polymer to the surface to produce about a 10-15 nm thick film.

Referring again to FIGS. 3 and 4, in another embodiment, a neutralwetting random copolymer material 14′ can be applied after formation ofthe material layer 16′ and trenches 18′, which reacts selectively withthe trench floor 26′ (composed of the substrate 10′ material) and notthe trench sidewalls 22′ or ends 24′ (composed of the material layer16′). For example, a random copolymer (or appropriate blend ofhomopolymers with block copolymer surfactant) containing epoxide groupswill react selectively to terminal amine functional groups (e.g. —NH—and —NH₂) on silicon nitride and silicon oxynitride surfaces relative tosilicon oxide or silicon. In another example in which the trench floor26′ is silicon or polysilicon and the sidewalls 22′ are a material suchas an oxide (e.g., SiO_(x)), the trench floor 26′ can be treated to formH-terminated silicon and a random copolymer material 14′ (e.g.,PS-r-PVP, PS-r-PMMA, etc.) can be formed in situ only at the floorsurface.

In another embodiment, a neutral wetting surface (e.g., for PS-b-PMMAand PS-b-PEO) can be provided by grafting a self-assembled monolayer(SAM) of a trichlorosilane-base SAM such as3-(para-methoxyphenyl)propyltrichorosilane grafted to oxide (e.g., SiO₂)as described, for example, by D. H. Park, Nanotechnology 18 (2007), p.355304.

In a further embodiment, a neutral wetting random copolymer ofpolystyrene (PS), polymethacrylate (PMMA) with hydroxyl group(s) (e.g.,2-hydroxyethyl methacrylate (P(S-r-MMA-r-HEMA)) (e.g., about 58 wt % PS)can be can be selectively grafted to a substrate 10 (e.g., an oxide) asa neutral wetting material 14 about 5-10 nm thick by heating at about160° C. for about 48 hours. See, for example, In et al., Langmuir, 2006,22, 7855-7860.

In yet another embodiment, a blend of hydroxyl-terminated homopolymersand a corresponding low molecular weight block copolymer can be grafted(covalently bonded) to the substrate to form a neutral wetting interfacelayer (e.g., about 4-5 nm) for PS-b-PMMA and PS-b-P2VP, among otherblock copolymers. The block copolymer can function to emulsify thehomopolymer blend before grafting. For example, an about 1 wt % solution(e.g., in toluene) of a blend of about 20-50 wt % (or about 30-40 wt %)OH-terminated homopolymers (e.g., M_(n)=6K) and about 80-50 wt % (orabout 70-60 wt %) of a low molecular weight block copolymer (e.g.,5K-5K) can be spin-coated onto a substrate 10 (e.g., SiO₂), heated(baked) (e.g., at 160° C.), and non-grafted (unbonded) polymer materialremoved, for example, by a solvent rinse (e.g., toluene). For example,the neutral wetting material can be prepared from a blend of about 30 wt% PS-OH (M_(n)=6K) and PMMA-OH (M_(n)=6K) (weight ratio of 4:6) andabout 70 wt % PS-b-PMMA (5K-5K), or a ternary blend of PS-OH (6K),P2VP-OH (6K) and PS-b-2PVP (8K-8K), etc.

A surface that is neutral wetting to PS-b-PMMA can also be prepared byspin-coating a blanket layer of a photo- or thermally cross-linkablerandom copolymer such as a benzocyclobutene- orazidomethylstyrene-functionalized random copolymer of styrene and methylmethacrylate (e.g., poly(styrene-r-benzocyclobutene-r-methylmethacrylate (PS-r-PMMA-r-BCB)). For example, such a random copolymercan comprise about 42 wt % PMMA, about (58−x) wt % PS and x wt % (e.g.,about 2-3 wt %) of either polybenzocyclobutene orpoly(para-azidomethylstyrene)). An azidomethylstyrene-functionalizedrandom copolymer can be UV photo-crosslinked (e.g., 1-5 MW/cm² exposurefor about 15 seconds to about 30 minutes) or thermally crosslinked(e.g., at about 170° C. for about 4 hours) to form a crosslinked polymermat as a neutral wetting material 14. A benzocyclobutene-functionalizedrandom copolymer can be thermally crosslinked (e.g., at about 200° C.for about 4 hours or at about 250° C. for about 10 minutes).

As illustrated in FIGS. 5-5B, a self-assembling, cylindrical-phase blockcopolymer material 28 having an inherent pitch at or about L_(o) (or aternary blend of block copolymer and homopolymers blended to have apitch at or about L_(B)) can be cast or deposited into the trenches 18to a thickness (t₁) at or about the L value of the block copolymermaterial 28 (e.g., about ±20% of L) such that after annealing (e.g.,FIG. 6A), the thickness (t₂) will be at or about the L value and theblock copolymer material 28 will self-assemble to form a single layer ofcylinders having a diameter of about 0.5*L (e.g., 5-50 nm, or about 20nm, for example) within a polymer matrix in a single row within eachtrench 18. The thickness of the block copolymer material 28 can bemeasured, for example, by ellipsometry techniques.

The block copolymer material 28 can be deposited by spin-casting(spin-coating) from a dilute solution (e.g., about 0.25-2 wt % solution)of the copolymer in an organic solvent such as dichloroethane (CH₂Cl₂)or toluene, for example. Capillary forces pull excess block copolymermaterial 28 (e.g., greater than a monolayer) into the trenches 18. Asshown, a thin layer or film 28 a of the block copolymer material 28 canbe deposited onto the material layer 16 outside the trenches 18, e.g.,on the spacers 20. Upon annealing, the thin film 28 a will flow into thetrenches 18 leaving a structureless brush layer on the material layer 16from a top-down perspective.

The block copolymer (BCP) material 28 is then heated above its glasstransition temperature under a vapor phase containing a partly saturatedconcentration of an organic solvent to cause the polymer blocks to phaseseparate and self-assemble according to the preferential and neutralwetting of the trench surfaces to form a self-assembled block copolymermaterial 30, as illustrated in FIGS. 6-6B. The appropriate partialpressure of solvent vapor to achieve a neutral wetting vapor interfaceat a particular temperature depends, at least in part, on the blockcopolymer that is used and can be determined empirically.

The block copolymer is heated at a thermal anneal temperature that isabove its glass transition temperature (T_(g)) but below thedecomposition or degradation temperature (T_(d)) of the block copolymermaterial. For example, a PS-b-PVP block copolymer material can beannealed at a temperature of about 150° C.-275° C. in a solvent vaporatmosphere for about 1-24 hours to achieve a self-assembled morphology.A PS-b-PMMA block copolymer material can be annealed at a temperature ofabout 150° C.-275° C. in a solvent vapor atmosphere for about 1-24 hoursto achieve a self-assembled morphology.

In most applications of a thermal anneal in a vacuum, an air interfaceis preferentially wetting to one of the polymer domains and the BCPmaterial does not orient into perpendicular structures. In embodimentsof the invention, during heating, the BCP material 28 is exposed tosolvent vapors of a “good” solvent for both blocks, that is, a neutralorganic solvent that solvates both the constituent blocks well.

In general, solvent annealing consists of two phases. In a first phase,the BCP material is exposed to a solvent vapor that acts to plasticizethe film and increase chain mobility causing the domains to intermingleand the loss of order inherent from casting the polymer material. Theorganic solvent that is utilized is based at least in part on itssolubility in the block copolymer material such that sufficient solventmolecules enter the block copolymer material to promote theorder-disorder transition of the polymer domains and enable the requiredmolecular rearrangement. Examples of solvents include aromatic solventssuch as benzene, toluene, xylene, dimethoxyethane, ethyl acetate,cyclohexanone, etc., and chlorinated solvents such as chloroform,methylene chloride, a chloroform/octane mixture, etc., among others. Ina second phase, the substrate is removed from the solvent vapor and thesolvent and solvent vapors are allowed to diffuse out of the polymermaterial and evaporate. The block copolymer material begins to “dry” asthe solvent evaporates from the material. The evaporation of the solventis highly directional and forms a solvent gradient from the “top”(surface) of the BCP material to the “bottom” of the BCP material at thetrench floor that induces orientation and self-assembly of structuresstarting at the air-surface interface, which is neutral wetting due tothe partial pressure of solvent at the interface, and driven downward tothe floor of the trench, with formation of perpendicular-orientedcylindrical domains 34 guided by the trench sidewalls and extendingcompletely from the air interface to the substrate surface (trenchfloor).

In embodiments of the invention, the substrate 10 and BCP material 28are heated above the boiling point of the solvent such that swelling ofthe BCP material 28 by the solvent is disallowed.

The use of a partly-saturated solvent vapor phase above the blockcopolymer material 28 provides a neutral wetting interface, similar tothe second phase of solvent annealing. The concentration of solvent inthe air immediate at the vapor interface with the BCP material 28 ismaintained at or under saturation to maintain a neutral wettinginterface such that both (or all) polymer blocks will equally wet thevapor interface. As both the air and trench floor 26 are neutralwetting, the domains will orient perpendicular throughout the filmlayer, with the preferential wetting sidewalls inducing lateral order.

The resulting morphology of the annealed block copolymer material 30(e.g., perpendicular orientation of cylinders 34) can be examined, forexample, using atomic force microscopy (AFM), transmission electronmicroscopy (TEM), scanning electron microscopy (SEM), among others.

In embodiments of the invention, the anneal is performed by globallyheating the block copolymer within the trenches in a solvent atmosphere.

In other embodiments, a zone annealing is conducted to anneal portionsor sections of the block copolymer material 28 in trenches on thesubstrate 10 by a localized application of thermal energy (e.g., heat).Zone annealing can provide rapid self-assembly of the block copolymermaterial (e.g., on the order of minutes).

For example, as depicted sequentially in FIGS. 6-8, the substrate 10 (ina vapor atmosphere) and a thermal or heat source 32 (or combined heatingand cooling source) can be moved relative to each other (e.g., arrow ←)such that heat is applied above (or underneath) the substrate 10. Only aportion of the BCP material 28 is initially heated above the glasstransition temperature and the heated zone is then “pulled” across thesubstrate 10 (or vice versa). For example, the thermal or heat source 32can be moved across the substrate 10 at a translational set speed (e.g.,about 0.05-10 μm/second using a mechanism such as a motorizedtranslation stage (not shown). Pulling the heated zone across thesubstrate 10 (or vice versa) can result in faster processing and betterordered structures relative to a global thermal anneal.

In some embodiments, a hot-to-cold temperature gradient can be providedover (or under) the substrate such that a certain portion of thesubstrate is heated and then cooled, which can be at a controlled rate.In other embodiments, the substrate can be exposed to a cold-to-hottemperature gradient to anneal the BCP material, followed by cooling.

In other embodiments, the BCP material can be heated above and thencooled below the order-disorder temperature (but above the glasstransition temperature), for example, to remove (melt out) defects andallow the material to recrystallize provided that the order-disordertemperature (T_(o-d)) is less than the decomposition temperature (T_(d))of the block copolymer material. The order-disorder temperature isdefined by the temperature dependence of the block copolymer, Chi value,the total number of monomers per chain, and the monomer composition.

Only those portions of the block copolymer material that are heatedabove the glass transition temperature (T_(g)) of the component polymerblocks will self-assemble, and areas of the material that were notsufficiently heated remain disordered and unassembled. For example, asillustrated in FIGS. 6-6B, initially, the block copolymer material 28within trench 18 a can be heated and annealed to form a self-assembledblock copolymer material 30 while the unannealed block copolymermaterial 28 within trenches 18 b, 18 c remains disordered. Only thoseportions of the block copolymer material 28 that are heated above theglass transition temperature (T_(g)) will self-assemble. A next portionof the substrate 10 can then be selectively heated, as shown in FIGS. 7and 7A, resulting in the self-assembly of the block copolymer materialwithin trench 18 b. A subsequent heating of the remaining areas of thesubstrate 10 can then be conducted, e.g., as depicted in FIGS. 8 and 8A.

Upon annealing, the cylindrical-phase block copolymer material 28 willself-assemble into a block copolymer material 30 (e.g., film) inresponse to the character of the block copolymer composition (e.g.,PS-b-PVP having an inherent pitch at or about L) and the boundaryconditions, including the constraints provided by the width (w_(t)) ofthe trench 18 and the wetting properties of the trench surfacesincluding a trench floor 26 that exhibits neutral or non-preferentialwetting toward both polymer blocks (e.g., a random graft copolymer),sidewalls 22 that are preferential wetting by the minority (preferred)block of the block copolymer (e.g., the PVP block), and the presence ofa neutral or non-preferential solvent (or in some embodiments, a film ormaterial that is neutral or non-preferential wetting) in contact withthe surface of the block copolymer material 28 in the trenches 18. Theanneal results in a row (or rows) of perpendicularly oriented cylinders34 of the minority polymer (preferred) block (e.g., PVP) within a matrix36 of the majority polymer block (e.g., PS), with the cylinders 34registered and parallel to the sidewalls 22 of the trenches 18. Thediameter of the cylinders 34 will generally be at or about 0.5*L (e.g.,about one-half of the center-to-center distance between cylinders). Inaddition, the minority (preferred) block (e.g., PVP) will segregate toand wet the preferential wetting sidewalls 22 and ends 24 of thetrenches 18 to form a thin interface or wetting brush layer 34 a havinga thickness generally about one-fourth of the center-to-center distancebetween adjacent cylinders 34. For example, a layer of the PVP blockwill wet oxide interfaces with attached PS domains directed outward fromthe oxide material.

In some embodiments, the self-assembled block copolymer material 30 isdefined by a single layer of an array of cylindrical domains (cylinders)34, each with a diameter at or about 0.5*L (e.g., about one-half of thecenter-to-center distance between cylinders), with the number (n) ofcylinders in the row according to the length (l_(t)) of the trench, andthe center-to-center distance (pitch distance, p) between each cylinderat or about L.

Optionally, after the block copolymer material is annealed and ordered,the copolymer material can be treated to crosslink the polymer segments(e.g., the PS segments) to fix and enhance the strength of theself-assembled polymer blocks. The polymers can be structured toinherently crosslink (e.g., upon exposure to ultraviolet (UV) radiation,including deep ultraviolet (DUV) radiation), or one of the polymerblocks of the copolymer material can be formulated to contain acrosslinking agent.

Generally, the film 28 a outside the trenches 18 a, 18 b, 18 c (e.g., onspacers 20) will not be thick enough to result in self-assembly.Optionally, the unstructured thin film 28 a can be removed, asillustrated in FIGS. 8 and 8A, for example, by an etch technique or aplanarization process to provide an about uniformly flat surface. Forexample, the trench regions can be selectively exposed through a reticle(not shown) to crosslink only the annealed and self-assembled blockcopolymer material 30 within the trenches 18 a, 18 b, 18 c, and a washcan then be applied with an appropriate solvent (e.g., toluene) toremove the non-crosslinked portions of the block copolymer material 28(e.g., on the spacers 20), leaving the registered self-assembled blockcopolymer material 30 within the trenches 18 a, 18 b, 18 c and exposingthe surface of the material layer 16 above/outside the trenches 18 a, 18b, and 18 c. In another embodiment, the annealed, block copolymermaterial 30 can be crosslinked globally, a photoresist material can beapplied to pattern and expose the areas of the copolymer material 28 aoutside the trench regions, and the exposed portions of the copolymermaterial 28 a can be removed, for example, by an oxygen (O₂) plasmatreatment.

Referring to FIG. 9, in another embodiment of a method of the invention,a thermal anneal is conducted while applying a non-preferentiallywetting material 37′ to the surface of the block copolymer (BCP)material 28′ in the trenches. In some embodiments, thenon-preferentially wetting material 37′ is composed of a solid material,which can be physically placed onto the BCP material 28′, for example, asoft, flexible or rubbery solid material such as a cross-linked,poly(dimethylsiloxane) (PDMS) elastomer (e.g., SYLGARD® 184 byDow-Corning) or other elastomeric polymer material (e.g., silicones,polyurethanes, etc.), which provides an external surface that is neutralwetting. The solid material can be derivatized (e.g., by grafting arandom copolymer) such that it presents a neutral wetting surface.

With the non-preferentially wetting material 37′ in contact with thesurface of the block copolymer material 28′, a thermal annealing processis conducted (arrows ↓, FIGS. 9A and 9B) to cause the polymer blocks tophase separate in response to the preferential and neutral wetting ofthe trench surfaces and the non-preferential (neutral) wetting of theoverlying material 37′, and form a self-assembled block copolymermaterial 30′ as illustrated in FIGS. 10A and 10B.

After annealing, the non-preferentially wetting material 37′ can beremoved from contact with the annealed, block copolymer material 30′(arrow ↑) as depicted in FIG. 10A. A PDMS or other elastomeric materiallayer can be removed, for example, by lifting or peeling the materialfrom the surface of the annealed, block copolymer material 30′.Additionally, a solvent such as water, alcohols, and the like, which iscompatible with and does not dissolve the block copolymer material 30′,can be applied (e.g., by soaking) to permeate and swell the elastomericmaterial (e.g., PDMS) to enhance physical removal. A dilute fluoridesolution (e.g., NH₄F, HF, NaF, etc.) can also be applied to etch anddissolve a PDMS material to remove it from the annealed polymermaterial.

Following self-assembly, the pattern of perpendicular-oriented cylinders34′ that is formed on the substrate 10′ can then be further processed asdesired, for example, to form an etch mask for patterning nanosizedfeatures into the underlying substrate 10′ through selective removal ofone block of the self-assembled block copolymer. Since the domain sizesand periods (L) involved in this method are determined by the chainlength of a block copolymer (MW), resolution can exceed other techniquessuch as conventional photolithography. Processing costs using thetechnique is significantly less than extreme ultraviolet (EUV)photolithography, which has comparable resolution.

For example, as illustrated in FIGS. 11-11B, in one embodiment, an etchmask 38 can be formed by selectively removing the cylindrical polymerdomains 34 of the self-assembled block copolymer material 30 to produceopenings 40 in the polymer matrix 36 (e.g., PS) to expose the underlyingsubstrate 10 at the trench floors 26. For example, the cylindricaldomains 34 can be removed by a selective wet etch (e.g., PMMA and PLA byUV exposure/acetic acid development, PLA by aqueous methanol mixturecontaining sodium hydroxide, PEO by aqueous hydroiodic acid or water,etc.) or by a selective reactive ion etch (RIE) process. In embodimentsin which the block copolymer includes a cleavable linker group, the filmcan be exposed to a solvent selective to the minor domain, for example,an alcohol for PVP, water for PEO or PLA, and acetic acid for PMMA, thatcontains a cleaving agent to remove (e.g., wash out) the minor domain.As depicted in FIGS. 12-12B, the remaining porous polymer (e.g., PS)matrix 36 can then be used as a lithographic template or mask to etch(arrows ↓↓) a series of cylindrical-shaped openings or contact holes 42in the nanometer size range (e.g., about 10-100 nm) to the conductivelines 12 or other active area (e.g., semiconducting region, etc.) in theunderlying substrate 10 (or an underlayer). The openings 42 can beformed, for example, using a selective reactive ion etching (RIE)process.

Further processing can then be performed as desired. For example, asdepicted in FIGS. 13-13B, the residual polymer matrix 36 can be removed(e.g., PS by an oxidation process such as a plasma O₂ etch) and theopenings 42 of substrate 10 can be filled with a material 44 such as ametal or metal alloy such as Cu, Al, W, Si, and Ti₃N₄, among others, toform arrays of cylindrical contacts to the conductive lines 12. Thecylindrical openings 42 in the substrate 10 can also be filled with ametal-insulator-metal stack to form capacitors with an insulatingmaterial such as SiO₂, Al₂O₃, HfO₂, ZrO₂, SrTiO₃, and the like.

Embodiments of the invention utilize a thermal anneal process incombination with solvent annealing, which can provide faster processingthan with a solvent anneal alone and expands the types of blockcopolymers (BCPs) that can be processed to substantially all BCPs. Inembodiments using a zone annealing in combination with an organicsolvent atmosphere, a wide range of block copolymers can be processed toform perpendicular-oriented nanostructures (e.g., cylinders) and at arapid rate.

In addition, methods of the disclosure provide a means of generatingself-assembled diblock copolymer films composed ofperpendicular-oriented cylinders in a polymer matrix. The methodsprovide ordered and registered elements on a nanometer scale that can beprepared more inexpensively than by electron beam lithography, EUVphotolithography or conventional photolithography. The feature sizesproduced and accessible by this invention cannot be easily prepared byconventional photolithography. The described methods and systems can bereadily employed and incorporated into existing semiconductormanufacturing process flows and provide a low cost, high-throughputtechnique for fabricating small structures.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement that is calculated to achieve the same purpose maybe substituted for the specific embodiments shown. This application isintended to cover any adaptations or variations that operate accordingto the principles of the invention as described. Therefore, it isintended that this invention be limited only by the claims and theequivalents thereof. The disclosures of patents, references andpublications cited in the application are incorporated by referenceherein.

What is claimed is:
 1. A method of forming a nanostructured polymermaterial, comprising: thermally annealing a block copolymer material incontact with a non-preferentially wetting material to cause polymerblocks of the block copolymer material to phase separate and form aself-assembled block copolymer material within a trench, thenon-preferentially wetting material over the block copolymer material.2. The method of claim 1, wherein thermally annealing a block copolymermaterial in contact with a non-preferentially wetting materialcomprises: zone heating a first section of a block copolymer material tocause the first section to phase separate and self-assemble, and thensubsequently heating remaining sections of the block copolymer materialto cause the remaining sections to phase separate and self-assemble. 3.The method of claim 1, further comprising removing thenon-preferentially wetting material to expose the self-assembled blockcopolymer material within the trench.
 4. The method of claim 3, furthercomprising applying a solvent to the non-preferentially wetting materialto enhance removal.
 5. The method of claim 1, wherein thermallyannealing a block copolymer material in contact with anon-preferentially wetting material comprises thermally annealing theblock copolymer material in contact with a non-preferentially wettingsolid material.
 6. The method of claim 1, wherein thermally annealing ablock copolymer material in contact with a non-preferentially wettingmaterial comprises thermally annealing the block copolymer material incontact with an elastomeric material.
 7. The method of claim 1, whereinthermally annealing a block copolymer material in contact with anon-preferentially wetting material comprises thermally annealing theblock copolymer material in contact with a poly(dimethylsiloxane)elastomer, a silicone, or a poly(urethane).
 8. The method of claim 1,wherein thermally annealing a block copolymer material in contact with anon-preferentially wetting material comprises thermally annealing theblock copolymer material in contact with a solid elastomeric material.9. A method of forming a nanostructured material, comprising: thermallyannealing a block copolymer material in contact with anon-preferentially wetting solid material to cause polymer blocks of theblock copolymer material to phase separate and form a self-assembledblock copolymer material within a trench in a first material overlying asecond material; removing the non-preferentially wetting solid materialto expose the self-assembled block copolymer material; crosslinking afirst block of the self-assembled block copolymer material; removing asecond block of the self-assembled block copolymer material to formopenings extending through the self-assembled block copolymer material;and removing at least a portion of the second material through theopenings to form openings in the second material.
 10. The method ofclaim 9, wherein thermally annealing a block copolymer material incontact with a non-preferentially wetting solid material to causepolymer blocks of the block copolymer material to phase separate andform a self-assembled block copolymer material comprises forming theself-assembled block copolymer material comprising cylindrical domainsof a first polymer block in a matrix of a second polymer block.
 11. Themethod of claim 9, wherein removing at least a portion of the secondmaterial through the openings comprises etching portions of the secondmaterial through the openings.
 12. The method of claim 9, furthercomprising forming a metal or metal alloy in the openings in the secondmaterial.
 13. The method of claim 9, further comprising removing thecrosslinked first block of the self-assembled block copolymer material.14. A method of forming a nanostructured polymer material, comprising:applying a non-preferentially wetting material to a top surface of ablock copolymer material, the block copolymer material within trenchesin a first material on a second material; and thermally annealing theblock copolymer material to form a self-assembled block copolymermaterial within the trenches.
 15. The method of claim 14, whereinapplying a non-preferentially wetting material to a surface of a blockcopolymer material comprises applying the non-preferentially wettingmaterial to the surface of a block copolymer material comprisingcylindrical domains of a first block of the block copolymer materialwithin a matrix of a second block of the block copolymer material. 16.The method of claim 15, wherein thermally annealing the block copolymermaterial to form a self-assembled block copolymer material within thetrenches comprises forming the cylindrical domains perpendicular to afloor of the trenches and extending through a thickness of theself-assembled block copolymer material in a single array for the lengthof the trenches.
 17. The method of claim 14, wherein applying anon-preferentially wetting material to a surface of a block copolymermaterial comprises applying a wetting material that is non-preferentialto any block of the block copolymer material.